THE ACOi'STir XHh'VI- !)7<j 



with the buccal branches of the seventh nerve; with the /ygotnat ico-facial branch 

 (if the zygoma) ic nerve (the orbital hratirh of the maxillary nerve) ; with the supra - 

 orbital and lachrymal lira riches of t he oj)hthalmic nerve, and with the palpebral t wigs 

 of the maxillary. They supply both eyelids and the orbicularis oculi and zygoma) icus 

 (fig. 706). 



The buccal (infra-orbital and buccal) branches arise sometimes from the 

 lower terminal division and sometimes from lioth the upper and the lower terminal 

 divisions. The buccal branches, passing forwards upon the masseterand underneath 



the zygomaticus and quadratus labii Buperioria, an&atomoae with the zygomatic and 



marginal mandibular (supra-mandibular) branches of the seventh nerve, with the 

 buccinator (long buecal) branch of the fifth ncrv(>. and with the terminal branches of 

 the maxillary nerve, forming with the last-named nerve the infra-orbital plexus. 

 They supply the zygomatlCUB, risorins. quadratus lal.)ii superioris. caninus, buccin- 

 ator, incisivi, orbicularis oris, triangularis, quadratus labii ini'erioris. and the muscles 

 of the nose (fig. 705). 



The marginal mandibular (supra-mandibular) branch, passing downwards 

 and forwards under cover of the risorius and the depressors of the lower lip, com- 

 municates with the buccal branches and with the ramus colli of the facial nerve, and 

 with the mental branch of the mandibular nerve. It supplies the quadratus labii 

 inferioris and mentalls. 



The ramus colli (infra-mandibular branch) runs downwards and forwards 

 under cover of the platysma. which muscle it innervates (fig. 705). Beneath the 

 platysma it forms one or more communicating loops, near its commencement, with 

 the great auricular nerve, and longer loops, lower down, with the superficial cervical 

 nerve. 



Central Connections. The superior extension of the nucleus of termination of the sensory 

 portion of the glosso-pharyngeal nerve, in which the film's of the pars intermedia of the facial 

 ii'iniin.itc. is MSMiciatcd with the somccsthetic area of the cortex cerebri by the medial lemnisrus 

 I fillet ) of tin- same arid opposite sides, and with the motor nuclei of the other cranial nerves by 

 the medial longitudinal fasciculus. The motor nucleus (nucleus of origin) of the facial is :i 

 ci.itcd with the s(im:i'sthetic area (lower third of the anterior central gyrus) by way of the pyr- 

 amidal fasciculi of the same and opposite sides, and with the nuclei of the other cranial nerves 

 liy way of the medial longitudinal fasciculus. 



THE EIGHTH NERVE THE ACOUSTIC OR AUDITORY 



Two distinct sets of fibres are contained in each acoustic nerve considered as a 

 whole. They comprise the vestibular and cochlear divisions of the nerve, which 

 could be well considered as separate cranial nerves. Both divisions are purely sen- 

 sory in nature, that is, the}' are composed of afferent fibres, but, since both their 

 peripheral distribution and their central connections are different, they must be 

 described separately. They are distinct at their superficial attachment to the 

 lateral aspect of the medulla oblongata at the inferior margin of the pons, the vesti- 

 bular division being.medial and ventral to the restiform body and just lateral to the 

 pars intermedia of the facial, while the cochlear division is more lateral and arches 

 around the dorsal surface of the restiform body. However, from near the medulla 

 to the bottom of the internal acoustic (auditory) meatus the two divisions are 

 blended into a common nerve-trunk which runs outwards, anteriorly, and upwards, in 

 company with the facial nerve and the internal auditory artery, which course along 

 its upper surface and are partially enclosed with it in a sheath of connective tissue. 

 At the bottom of the internal auditory meatus the nerve is again separated into its 

 two divisions, the vestibular above and the cochlear below. 



The vestibular division or nerve. The fibres of the vestibular division are dis- 

 tributed to the utriculus. the sacculus, and to the ampulke of the three semicircular 

 canals. None of them terminate in the cochlea, and therefore they are not con- 

 sidered auditory in function, hut rather as having to do with the phenomena of equili- 

 bration or the sense of position of the body. In the internal auditory meatus the 

 vestibular division is connected by small filaments with the pars intermedia of the 

 facial nerve, both giving fibres to and probably receiving fibres from the geniculate 

 ganglion. At the bottom of the meatus there is interposed in the vestibular division 

 its ganglion of origin, the vestibular ganglion (ganglion of Scarpa). I'nlike the 

 ordinary spinal ganglion, to which it corresponds, the vestibular ganglion consists 



